A developing tank is in the analog photography employed instrument for development of films . This means light-tight containers into which the light-sensitive material is normally placed in complete darkness. After sealing, the ambient light can be switched on and the development process can be carried out by filling / pouring out the necessary chemicals and moving accordingly. The coils of the film are prevented from sticking together either by a spiral insert (as in the photo) or by a nub tape, which has small bumps on the edge (so that the traces are not visible in the picture), which is wound up together with the film. To move the insert, turn it jerkily or tilt the entire can (for this purpose, the lid must be able to be closed watertight, e.g. with an additional cap).
Compared to the shell development in open containers, there is the advantage that you can work in ambient light. In addition, the movement of the can can be mechanized.
As a developing tank , a mostly semi-automatic or fully automatic developing machine is called.
A daylight box also allows loading in normal ambient light. It consists of two chambers, the actual developing tank and the film cartridge chamber. The film cartridge can be inserted in daylight, the film gate is inserted into the transport mechanism of the tank and the housing is closed. The film is then wound into the can, cut off at the end with an integrated cutting device, depending on the model, and can then be developed.
As a developing sleeve cylindrical containers are for the processing of photographic paper , respectively. In contrast to tray development , drum development allows the processing of bulky large formats with complete exclusion of light (e.g. for color papers) with very small amounts of chemicals (which in color processes usually have to be poured on after each use). In contrast to film developing cans, developing drums are always used horizontally: only when they are tilted horizontally do the previously introduced liquids come into contact with the photo paper lying on the inner wall. The paper is evenly wetted by manually rolling the drum on a work surface or by automatically rolling it in the temperature-controlled water bath of a developing machine.